Dr. Lukas of Northwestern University Feinberg School of Medicine received honorariums from AbbVie as a guest speaker, from NewLink Genetics and Reneuron for consulting work, and from Monetris as an advisory board member.

)Originally released March 14, 1995; last updated June 20, 2017; expires June 20, 2020

This article includes discussion of dermoid and epidermoid tumors, dermoid cyst, epidermoid cyst, cholesteatoma, pearly tumor, dermoid tumors, and epidermoid tumors. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

In this article, the author reviews pathologies of dermoid and epidermoid tumors in the brain and spine. Epidermoid and dermoid cysts arise from ectopic ectodermal cells that are retained within the neural groove during early gestation. These tumors have varying presentations that depend on location of the mass. Symptoms range from isolated cranial neuropathy to aseptic meningitis after cyst rupture. Imaging findings are typically diagnostic, with CT and MRI findings appearing similar to arachnoid cysts, but with restricted diffusion on diffusion-weighted MRI. With complete resection, recurrence is atypical. Incompletely resected masses are prone to recurrence as the cyst wall continues to produce keratin. However, as these are slow growing lesions, they are occasionally treated with debulking alone to avoid injury to the surrounding structures, including nerves and blood vessels. Extensive resections are associated with high rates of early or delayed postoperative deficits. Total resection is possible only in 50% to 70% of cases. Malignant transformation to squamous cell carcinoma occurs rarely.

Key points

• Most epidermoids and dermoids are developmental in origin, forming between the third and fifth week of embryonic development.

• The MRI characteristics of epidermoids and dermoids are usually diagnostic, but 5% have atypical appearance.

• Epidermoids and dermoids are potentially curable with surgery, but malignant transformation can be seen rarely.

• Aseptic meningitis and ventriculitis may occur postoperatively if there is leaking of cholesterol crystals.

• Perioperative morbidity (20%) and mortality (7%) remains high, particularly if total resection is attempted as epidermoids often grow along nerves and blood vessels.

• Lesions are slow-growing, and late recurrence is common with incompletely resected tumors.

Historical note and terminology

The first description of an epidermoid has been attributed to Pinson, an artist in the School of Medicine in Paris, who created a wax model of a smooth cyst located at the cerebellopontine angle in 1807 (Mahoney 1936). It was not until 1829 that Jean Cruveilheir, a French pathologist, first recognized epidermoids as a specific entity and gave them the name "tumeur perleé" (Cruveilheir 1829). Dr. Müller described these masses as well, calling them "cholesteatomas" as they were seen to contain cholesterol (Soldati and Mudry 2001). Walter Dandy described epidermoid tumors as “the most beautiful tumor in the body” given their pearly appearance; whereas dermoid tumors have less of this appearance, containing hair and fat (Dandy 1945).

Epidermoid and dermoid tumors are no longer included amongst the tumors of the 2016 edition of the World Health Organization Classification of Tumors of the Central Nervous System (Louis 2016). Medical literature uses the terms "cysts" or "tumors" interchangeably to describe "epidermoids" and "dermoids." Along with craniopharyngiomas, Rathke cleft cysts, germinomas, and nongerminomatous germ cell tumors are referred to as "dysontogenetic," which means a defective development of an embryo (Niikawa et al 1992).

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